The exemplary embodiments described herein relate to diverting fluids that include a solids-free diverting agent that comprises degradable polyesters, and methods relating thereto.
Diverting agents may be used in a variety of subterranean treatments (e.g., drilling, stimulation treatments (e.g., fracturing treatments, matrix acidizing treatments), and cementing operations). For example, a producing portion of the subterranean formation can be stimulated by introducing an aqueous acid solution into the surrounding formation matrix to dissolve formation material or materials near the wellbore, thereby increasing its porosity and permeability and enhancing hydrocarbon production from that portion. To treat the producing portion effectively, a diverting agent is often placed in the more permeable portions to mitigate fluid flow into those portions and direct the placement of the desired treatment fluid into the producing portion.
Traditional diverting agents may be grouped into two general classifications: viscous-fluid diverting agents and mechanical diverting agents. In the former, typically, a relatively high viscosity fluid flows into a subterranean portion, creating a resistance that causes subsequent treatment fluids to be diverted to other portions of the formation. The viscous-fluid diversion methods are considered relatively easy to implement, but are generally thought not to be as effective as diverting agents that introduce a mechanical barrier. Additionally, high temperatures associated with greater depth in the subterranean formation can lead to increased instability of such viscosified fluids.
Mechanical diverting agents, which work by forming a physical barrier to flow, include particulate diverters. Particulate diverting agents often are suspended in a carrier fluid, often to a point of saturation to be pumped downhole. This carrier fluid is oftentimes introduced to the subterranean formation during a stimulation treatment. Traditional examples of particulate diverting agents are inorganic materials (such as rock salts) and polymeric materials. These particulate materials typically form a seal in the subterranean formation (e.g., by packing off perforation tunnels, plating off against a formation surface, plating off a hole behind a slotted liner, or packing along the surface of a hydraulic fracture), causing a subsequent treatment fluid to be diverted to other portions of the formation.
Because particulate diverting agents are suspended in a carrier fluid, the particulates tend to settle or segregate in the fluid, especially when the flow rate of the carrier fluid is reduced (e.g., as it penetrates into fractures and perforation in the subterranean formation). As a result, particulate diverting agents oftentimes are deposited primarily in near-wellbore portions of the subterranean formation. Further, because the diverting agents are particulates, their efficacy is limited by their size, especially in shale zones. That is, portions of the formation matrix with pore sizes smaller than the particle size cannot be penetrated though with the particulate diverting agents. These drawbacks can reduce the efficiency of the diverting fluids.